1. Field of the Invention
The present invention relates to a method for lighttightly packaging a stack of light-sensitive photographic sheets in a lighttight holder. The invention is in particular intended for a holder for daylight-loading large-format aluminium printing plates in a so-called computer-to-plate machine.
2. Description of the Prior Art
Aluminium printing-plate packages for daylight-loading printing plates in a computer-to-plate machine are known.
One known shipping package has the form of a cassette which can be loaded by the user directly into the machine. The machine has means for opening the cassette and taking out the plates one by one for their image-wise exposure by the laser system of the machine, and next their processing.
This known package is a composite structure of corrugated cardboard for the top and the bottom of the cassette, and a wooden frame for the side walls. Since the packaged plates are highly sensitive to dust and like particles, careful treatment of the inside surfaces of the package is required in order to keep it dustfree. Suitable treatments are lacquering or taping. A package as described above has been proposed by Creo Products Inc., Burnaby, Calif.
Another plate package has been disclosed in our co-pending EP Application Ser. No. 94 203 602.1 filed Dec. 12, 1994. It comprises a stack of plates lighttightly wrapped between two lighttight wrapping foils of a size larger than that of the plates, the flaps of the wrapping extending beyond the package being backfolded on the package and peripherally closed near their edges, the size of the flaps being such as to allow lighttight clamping of the wrapping sheets onto each other along a peripheral zone located within the peripheral closure. The operator must place this package in a cassette-like frame of the apparatus, and next cut off the sealed portion of the lighttight wrapper in order to open the package. This package is thus less convenient to handle.